Invertebrates, lacking IgG molecules, depend on adhesion proteins, lectins and other defense molecules for the removal of invading microorganisms. Limunectin, an intracellular phosphocholine binding protein isolated from Horseshoe crab amebocytes might play an important role in the defense mechanism. The gene coding for this protein has been isolated and sequenced; it consists almost entirely of 10 contiguous segments, 45 amino acids in length, with extensive homology. SDS-PAGE analysis reveals this protein to be a single polypeptide chain of about 50 kDa. It binds to PC in a calcium independent manner. It also binds to bacteria cells, fixed amebocytes, and a number of extracellular matrix molecules. The name Limunectin was given to this protein because of its structural and functional similarities to other adhesion molecules. Experiments are underway to express individual domain of Limunectin in E. coli in order to further study its structure-function relationship.